Abstract:Direct
Laser Deposition (DLD) is a blownpowder laser deposition
process which can be used to quickly produce fully-dense
metallic prototypes by a layered manufacturing method. DLD
can also be used to repair or modify high-value components.
In common with other laser deposition processes, variation
in the process parameters (traverse speed, powder flow rates
etc.) can cause height errors in the built part. Layer height
control methods are therefore a continually investigated
field.
Research carried out at Liverpool University has resulted
in a non-feedback layer height controlling process based
on controlling the shape of the powder streams emitted from
a four-port side feed nozzle. This method limits deposited
layer height by causing a sharp reduction of catchment efficiency
in the vertical plane at a fixed distance from the powder
feed nozzle, and is therefore capable of depositing a consistent
layer height in spite of power, powder flow or process velocity
variation. This paper examines the effects of altering the
configuration of a four port nozzle system on the shape
of the emitted powder streams and demonstrates the benefits
of using the derived `best' configuration in the production
of test samples. In addition, the effects upon microstructure
of parts generated in this fashion are discussed.